This proposal is focused on studying the relationship between functions and structure of the G-beta subunit of heterotrimeric G-protein, and identification of new proteins involved in the signal transduction through the G-beta-gamma complex in Dictyostelium. Using phenotypes of Dictyostelium as a simple biological "readout", I propose three screening procedures to isolate functional G-beta subunit. To establish the relationship between functions and structure of G-beta subunit, I propose to characterize the obtained G-beta mutants using different methods, and then classify them. The information from his study can potentially be applied to mammalian systems, in which gene knock-out is still difficult, to study functions of G-beta subunits in vivo. In order to identify novel components linking G protein to signaling pathways. l propose to isolate suppressor genes of mutant alleles of G-beta subunit in Dictyostelium. The long-term goal is to have a better understanding of the mechanism of G- protein-coupled signal transduction at a molecular level.